An Experimental Study of Compaction Grouting on Its Densification and Confining Effects

Compaction grouting (CPG) involves the injection of high viscosity mortar-type grout under relatively high pressure that displaces and compacts the soil in-place. Many case studies around the world prove the effectiveness of CPG to treat liquefiable soils. In these studies, mostly CPG has been developed and used on the basis of practical experiences, its densification and confining effects are not well understood until now. The objective of the present study is to bring out densification and confining effects of CPG. This paper presents a laboratory experimental study carried out to model a CPG treated ground. The study includes the experiments performed to decide appropriate consistency of grout material and appropriate relative contribution of factors such as overburden pressure, grout volume, injection speed and injection pressure that ensures efficient grouting. The effects of CPG are quantified in terms of lateral earth pressures and lateral displacements that are further defined in terms of coefficient of lateral earth pressure, K, and densification factor in the soil around grout column. This leads to a better understanding of its densification and confining effects. Although in practice, majority of the works with CPG have been related to its densification effect and lesser attention has been given to its confinement effect, in present experimental study, its confinement effect were prominent. Also at the farthest locations usually where field tests are carried out, its densification effect could not be found experimentally but its confinement effect was clear.